Análise espectroscópica detalhada de estrelas candidatas a gêmeas solares

Abstract

Solar twins are defined as stars with the same mass, age, atmospheric parameters (temperature, metalicity, surface gravity) luminosity, chemical composition, evolutionary state, chromospheric activity, Li depletion, and other characteristics as the Sun. Such objects may help answer the still lingering question of how typical the Sun is with respect to the local stellar population of middle-aged G-type stars. On the other hand, such a stars are presumably privileged candidates to possess planetary systems similar to our own, besides being natural places to look for telluric planets harboring life forms similar to those known to us, and for the SETI program researches. Upon identification of HD146233 as the best ever solar twin (Porto de Mello & da Silva (1997)), a following survey (da Silva (2000)) identified a number of further candidates to solar twin status among the G-type stars within 50 parsecs of the Sun. In this work, we investigate the best solar twin and solar analog candidates proposed by this survey. We perform a full and detailed spectroscopic fine analysis of such best candidates, uniformly based on high-resolution (R = 47.000) and high signal-to-noise ratio (S/N & 350) ESO/FEROS spectra. We determine their effective temperatures, Fe abundances, surface gravities and microturbulence velocities by the excitation & ionization equilibria of a large number of Fe lines. These are supplemented by determinations of effective temperatures based on photometric calibrations and the theoretical fitting of Hα spectra. We also determine the abundances of Si, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Y, Ba and Ce, along with their galactic velocity components and degree of chromospheric activity as judged by the absolute flux of Hα and Ca II H & K spectra. We also qualitatively assess their Li abundances. Finally, we obtain their masses and ages in theoretical HR diagrams. These data are massed into a complete analysis of their properties compared to the solar ones. We present a number of new solar twin candidates and discuss their properties in detail.